at
or
is shortage of liberties, and at
(or elsewhere taking a black liberty) by the same
(connect-and-die).
captures two stones, leaving equal number of liberties with Black to move...
And wins the capturing race by one move.
is a must.
Black can be even more direct - after the
stones are in a snapback.
Or if White defends the snapback, puts the white group into atari.
The atari at is wrong...
...when White plays the hane at , Black is stuck. If Black pushes at a, he is in self-atari.
The above solution(s) are incorrect. The vital point is . Once
is played, White must play at
to survive. Black then plays at
. White captures
with
to prevent Black from capturing it's group. At this point Black must play at
.
is not in atari so there is no need to solidify with 'a', for if Black did play at 'a', White would respond with 'b'. If Black plays at
, White will be captured and Black can live.
The statement above is wrong. After white has an eye and black does not. White can even play tenuki. If now black plays a white plays b and vice versa. This situation is called me-ari-me-nashi. Hans
Karl Knechtel, lavalyn, Scartol